Which gauges for track construction?

[John Palmer]

But written of course before the advent of functional plastic check rail chairs. Perhaps it needs updating to emphasize that when using these chairs it is the check rail which should be set using the gauge tools, not the running rail. The track gauge to the running rail is determined by the chair, not by using the track gauge tools

This, in part, is what prompted my enquiry. It seemed to me that the emboldened part of Martin's post represented a significant divergence from the technique applicable to the ply and rivet form of construction in universal use when I last made any track. It means that the choice of whether to introduce gauge widening into a turnout is made when you decide whether to use .8mm check chairs rather than .68mm. Quite different from soldered track construction.

[Martin Wynne]

It's worth bearing in mind that the 0.8mm check rail chairs provide gauge widening of only 0.12mm, i.e. to a track gauge of 18.95mm.

That's not very much. At the sort of sharp curves typically used in models, below 5.1/2 chains radius ( = 1452mm, 4ft-9in, scale), the prototype allows widening of 3/4" ( = 0.25mm scale). Between 5.1/2 chains and 7 chains radius ( = 1848mm, 6ft-1in, scale) the prototype allows widening of 1/2" ( = 0.17mm scale).

So using the 0.8mm chairs to apply widening of only 0.12mm is being a bit timid, and may not be enough to work as intended for long-wheelbase rolling stock.

It may be better to fix the rails by other means, cutting the check chairs in half and adding them cosmetically afterwards.

Note also that bullhead check rails are not inclined at 1:20, they are always vertical, and always fixed with wooden keys rather than spring steel keys.

Martin.

[grovenor-2685]

Note that the CC chairs herehave a range of 4 flangeway widths.
Keith